Sheet processing apparatus, sheet processing apparatus control method, and computer-readable storage medium

ABSTRACT

A method for controlling a sheet processing apparatus configured to convey a sheet fed from any one of a plurality of sheet feed units includes detecting curling of the sheet fed from any one of the plurality of sheet feed units, and specifying a sheet feed unit that has fed the sheet having the detected curling from among the plurality of sheet feed units.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet processing apparatus, a sheet processing apparatus control method, and a computer-readable storage medium.

2. Description of the Related Art

A conventional electrophotographic image forming apparatus, which feeds a sheet from a sheet feed unit and forms an image on the sheet conveyed therethrough, transfers a toner image formed on a photosensitive drum onto the sheet fed from the sheet feed unit and fixes the toner image on the sheet with a fixing device. The fixing device fixes the toner image on the sheet by applying pressure and heat thereon. In this regard, the sheet may be physically curled (deformed) during fixing the toner image on the sheet.

If a sheet is curled, the quality of a resulting processed product may degrade. Furthermore, the maximum quantity of the sheet to be stacked on a sheet discharge tray maybe reduced. That is, if curled sheets are stacked, the total thickness of the stacked sheet bundle may become greater than that of uncurled sheet bundle. Accordingly, if curled sheets are stacked, the maximum quantity of stackable sheets may become small. Furthermore, the stability of the stacked sheet bundle may degrade.

In this regard, in order to correct curling of a sheet, Japanese Patent Application Laid-Open No. 2008-013284 discusses an image forming apparatus that corrects the curling of a sheet by using a curling correction roller installed in a sheet conveyance path after fixing the toner image on the sheet with a fixing device. By using the above-described conventional image forming apparatus, a user can adjust the amount of correcting curling of a sheet with the curling correction roller.

However, if a plurality of sheet feed units is provided, the conventional image forming apparatus or the method discussed in Japanese Patent Application Laid-Open No. 2008-013284 does not determine from which sheet feed unit the curled sheet has been fed in adjusting the sheet curling correction amount or executing other processing.

Accordingly, with the above-described conventional method, the user cannot easily recognize the sheet feed unit that has fed the curled sheet. Furthermore, the user cannot easily input a curling correction amount for the sheet fed from the sheet feed unit.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a sheet processing apparatus configured to convey a sheet fed from any one of a plurality of sheet feed units includes a curl detecting unit configured to detect curling of the sheet fed from any one of the plurality of sheet feed units, and a specifying unit configured to specify a sheet feed unit that has fed the sheet having the curling detected by the curl detecting unit from among the plurality of sheet feed units.

Further features and aspects of the present invention will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the invention and, together with the description, serve to describe the principles of the present invention.

FIG. 1 illustrates an exemplary configuration of an image forming system according to an exemplary embodiment of the present invention.

FIG. 2 illustrates an exemplary configuration of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 3 illustrates an exemplary configuration of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 4 illustrates an example of a curling correction roller pair according to an exemplary embodiment of the present invention.

FIG. 5 illustrates an example of a curling correction roller pair according to an exemplary embodiment of the present invention.

FIG. 6 illustrates an example of a paper feed deck according to an exemplary embodiment of the present invention.

FIG. 7 illustrates an example of a large-capacity stacker according to an exemplary embodiment of the present invention.

FIG. 8 illustrates an exemplary configuration of a saddle stitch binding machine according to an exemplary embodiment of the present invention.

FIG. 9 illustrates an example of an operation unit according to an exemplary embodiment of the present invention.

FIG. 10 illustrates an example of a display screen displayed on a touch panel according to an exemplary embodiment of the present invention.

FIG. 11 illustrates an example of a display screen displayed on the touch panel according to an exemplary embodiment of the present invention.

FIG. 12 illustrates an example of a display screen displayed on the touch panel according to an exemplary embodiment of the present invention.

FIG. 13 is a flowchart illustrating exemplary control processing according to an exemplary embodiment of the present invention.

FIG. 14 is a flowchart illustrating exemplary control processing according to an exemplary embodiment of the present invention.

FIG. 15 illustrates an example of a job management table displayed on the touch panel according to an exemplary embodiment of the present invention.

FIG. 16 illustrates an example of a display screen displayed on the touch panel according to an exemplary embodiment of the present invention.

FIG. 17 illustrates an example of a display screen displayed on the touch panel according to an exemplary embodiment of the present invention.

FIG. 18 illustrates an example of a display screen displayed on the touch panel according to an exemplary embodiment of the present invention.

FIG. 19 illustrates a sheet discharge operation according to an exemplary embodiment of the present invention.

FIG. 20 illustrates an example of a job management table according to an exemplary embodiment of the present invention.

FIG. 21 illustrates an example of a display screen displayed on the touch panel according to an exemplary embodiment of the present invention.

FIG. 22 illustrates an example of a display screen displayed on the touch panel according to an exemplary embodiment of the present invention.

FIG. 23 illustrates a sheet discharge operation according to an exemplary embodiment of the present invention.

FIG. 24 illustrates an example of a job management table according to an exemplary embodiment of the present invention.

FIG. 25 is a flowchart illustrating exemplary control processing according to an exemplary embodiment of the present invention.

FIG. 26 is a flow chart illustrating exemplary control processing according to an exemplary embodiment of the present invention.

FIG. 27 illustrates an example of a display screen displayed on the touch panel according to an exemplary embodiment of the present invention.

FIG. 28 illustrates a sheet discharge operation according to an exemplary embodiment of the present invention.

FIG. 29 illustrates an example of a job management table according to an exemplary embodiment of the present invention.

FIG. 30 illustrates an example of a display screen displayed on the touch panel according to an exemplary embodiment of the present invention.

FIG. 31 illustrates a sheet discharge operation according to an exemplary embodiment of the present invention.

FIG. 32 illustrates an example of a display screen displayed on the touch panel according to an exemplary embodiment of the present invention.

FIG. 33 illustrates exemplary program code according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the present invention will now be herein described in detail below with reference to the drawings. It is to be noted that the relative arrangement of the components, the numerical expressions, and numerical values set forth in these embodiments are not intended to limit the scope of the present invention.

A first exemplary embodiment of the present invention will be described in detail below. FIG. 1 illustrates an exemplary configuration of an image forming system 1000 according to the present exemplary embodiment. The image forming system 1000 includes an image forming apparatus 100, to which a paper feed deck 50 a, a paper feed deck 50 b, a large-capacity stacker 200 a, a large-capacity stacker 200 b, and a saddle stitch binding machine 200 c are connected.

FIG. 2 illustrates an exemplary inner configuration of the image forming apparatus 100 of the image forming system 1000 according to the present exemplary embodiment. The image forming apparatus 100 illustrated in FIG. 1 is also illustrated in FIG. 2. Referring to FIG. 2, a paper feed deck 50 includes the paper feed decks 50 a and 50 b illustrated in FIG. 1. A sheet processing apparatus 200 includes the large-capacity stackers 200 a and 200 b and the saddle stitch binding machine 200 c, which are illustrated in FIG. 1.

The image forming apparatus 100 includes a control unit 201, a scanner unit 202, an operation unit 203, a compression/decompression unit 204, a read-only memory (ROM) 205, a random access memory (RAM) 206, a printer unit 207, a hard disk drive (HDD) 208, and an external interface (I/F) unit 209, which are in communication with one another.

The control unit 201 centrally controls the operation of and processing executed by the image forming system 1000. The ROM 205 stores a program loaded and executed by the control unit 201. The RAM 206 is used as a work area for the control unit 201. Furthermore, the RAM 206 stores a control table used in executing control processing.

The operation unit 203 includes a liquid crystal display (LCD) unit and a touch panel. The operation unit 203 can receive an instruction from a user and display a message to the user. The scanner unit 202 reads an image of a document and generates image data of the read document. The printer unit 207 prints the image data. The compression/decompression unit 204 performs compression and decompression processing on image data based on various compression formats, such as Joint Bi-level Image Experts Group (JBIG) or Joint Photographic Experts Group (JPEG).

The HDD 208 stores the image data read with the scanner unit 202 and page description language (PDL) data received from an external apparatus, such as a personal computer (PC), via the external I/F unit 209.

The control unit 201 of the image forming apparatus 100 executes a job, such as a copy job or a print job, by loading and executing the program from the ROM 205. Here, a “copy job” is a job for forming an image with the printer unit 207 based on the image data read with the scanner unit 202 according to a setting received from the operation unit 203. A “print job” is a job for forming an image with the printer unit 207 based on the image data received via the external I/F unit 209 according to a print setting that has been associated with and set on the image data.

Now, an image forming operation performed according to an instruction from the control unit 201 will be described in detail below with reference to a cross section of the image forming system 1000 illustrated in FIG. 3. FIG. 3 is a cross section that illustrates an example of the image forming apparatus 100, the paper feed deck 50, and the sheet processing apparatus 200 according to the present embodiment.

In the present exemplary embodiment, the image forming apparatus 100 is a 1D (single-drum) type color multifunction peripheral (MFP). However, the present invention is not limited to this. That is, a monochromatic MFP or a 4D (four-drum) type MFP can be used as the image forming apparatus 100.

Referring to FIG. 3, an auto document feeder (ADF) 301 separates a document set on a stacking surface of a document tray page by page from the first page. Then, the ADF 301 feeds the document onto a document positioning glass to scan the document with a reading unit 302. The reading unit 302 reads an image on the document that has been conveyed onto the document positioning glass and converts the read document image into image data with an image sensor, such as a charge-coupled device (CCD).

A ray, such as a laser beam, which has been modulated according to the image data, is made incident on a rotating polygonal mirror 303. The ray reflected from the rotating polygonal mirror 303 then falls on the surface of a photosensitive drum 304 via a reflection mirror as reflection scanning light to form a latent image on the surface of the photosensitive drum 304. The latent image formed on the surface of the photosensitive drum 304 with the ray is then developed with toner.

Furthermore, the image forming apparatus 100 conveys a sheet fed from any one of paper feed cassettes 401 through 408, each of which is an example of a paper feed unit, to a registration roller 316. The image forming apparatus 100 further conveys the sheet onto a transfer drum 305 to transfer the toner image on the photosensitive drum 304 onto the sheet on the transfer drum 305.

By serially performing a series of image forming processing on toners of colors of yellow (Y), magenta (M), cyan (C), and black (K), a full color image is formed. After performing four-image forming processing, a sheet on the transfer drum 305, onto which a full color image has been formed, is then separated from the transfer drum 305 by a separation claw 306. Then, the separated sheet is conveyed to a fixing device 308 by a pre-fixing conveyance unit 307.

The fixing device 308 includes rollers and a belt in combination with one another. Furthermore, the fixing device 308 includes therein a heat source such as a halogen heater. The fixing device 308 applies heat and pressure to the toner on the sheet having the transferred toner image. Thus, the toner on the sheet having the toner image is fused and fixed.

A sheet discharge flapper 309 can swing around an axis. The sheet discharge flapper 309 swings to regulate the direction of conveying a sheet. When the sheet discharge flapper 309 swings clockwise in FIG. 3, the sheet is conveyed in a straight direction. Then, the sheet is conveyed to a paper discharge roller 310 and is then discharged to the large-capacity stacker 200 a by the paper discharge roller 310.

On the other hand, in forming images on both sides of the sheet (two-sided printing), the sheet discharge flapper 309 swings counterclockwise in FIG. 3 to change the path for conveying the sheet to a downward direction. Thus, the sheet is conveyed to a two-sided conveyance unit. The two-sided conveyance unit includes a reversal flapper 311, a reversal roller 312, a reversal guide 313, and a two-sided tray 314.

The reversal flapper 311 swings around an axis and regulates the direction of conveying the sheet. In performing a two-sided print job, the control unit 201 performs the following control. That is, the control unit 201 performs control so that the reversal flapper 311 swings counterclockwise in FIG. 3 to convey the sheet, whose first surface has been already printed, into the reversal guide 313 via the reversal roller 312.

Then, the control unit 201 temporarily stops the reversal roller 312 in the state where a trailing edge of the sheet is pinched by a reversal roller 324. Then, the control unit 201 allows the reversal flapper 311 to swing counterclockwise in FIG. 3. Furthermore, the control unit 201 allows the reversal roller 324 to rotate in a reverse direction.

As described above, the control unit 201 performs control so that the sheet is switched back to be conveyed. The control unit 201 performs control to guide the sheet to the two-sided tray 314 in the state where the leading edge and trailing edge of the sheet have been changed in position.

The two-sided tray 314 temporarily stacks the sheet that has been conveyed thereto as described above. Then, the sheet temporarily stacked on the two-sided tray 314 is conveyed again to the registration roller 316 by a paper refeed roller 315. At this time, the sheet is fed with a surface thereof opposite to the first surface used in the transfer processing facing the photosensitive drum 304.

Then, the control unit 201 performs control to form an image on the second surface of the sheet as in the processing described above.

Thus, images are formed on both sides of the sheet. Then, the sheet having the image formed thereon is subjected to fixing processing by the fixing device 308. After that, the sheet having the image fixed thereon is conveyed to the paper discharge roller 310 again and conveyed to the large-capacity stacker 200 a via the paper discharge roller 310.

In the image forming apparatus 100, which forms an image by electrophotographic processing, a sheet may be physically curled during fixing the toner on the sheet with the fixing device 308. A sheet may be curled when the toner that has been transferred on the sheet is fused by the heat applied by the fixing device 308 and is later condensed after the heated toner is cooled down. In this regard, the present exemplary embodiment corrects the curling of the sheet on which the toner has been fixed by the fixing device 308 with the curling correction roller pairs 340 and 341.

The amount of curling of a sheet may differ according to the type of the sheet. Therefore, the amount of curling corrected with the curling correction roller pairs 340 and 341 should be changed according to the type of the sheet. In this regard, the present exemplary embodiment allows the user to set the curling correction amount independently and differently for each paper feed cassette by operating the operation unit 203. Thus, the user can correct the curling of the sheet according to the curling correction amount differently and appropriately set for each paper feed cassette.

In the present exemplary embodiment, the curling of the sheet fed from the paper feed cassettes is corrected by two types of curling correction roller pairs. Among the two types of curling correction roller pairs, the upward curling correction roller pair 341 applies the correction force for bending both edges of the sheet downward to the sheet in the sheet conveyance direction to correct upward curling of the sheet, in which both edges of the sheet are curled upward in the sheet conveyance direction. On the other hand, the downward curling correction roller pair 340 applies the correction force for bending both edges of the sheet upward to the sheet in the sheet conveyance direction to correct downward curling of the sheet, in which both edges of the sheet are curled downward in the sheet conveyance direction.

The upward curling correction roller pair 341 will be described in detail below with reference to FIG. 4.

Referring to FIG. 4, the upward curling correction roller pair 341 is constituted by a sponge roller 501 having a soft surface and a lower roller 502, which is pressed against and engages in the sponge roller 501. A roller shaft 503 of the sponge roller 501 is urged upward against a frame (not illustrated) by an urging unit (not illustrated). The roller shaft 503 can be moved in a vertical direction while being supported by the frame.

A bearing 504 contacts the roller shaft 503 from above. An eccentric cam 505 contacts the bearing 504 from above. When the eccentric cam 505 rotates around the shaft 506 from a position illustrated in FIG. 4, the bearing 504 is pressed downward due to the shape of the eccentric cam 505. At the same time, the roller shaft 503 is pressed down, together with the sponge roller 501, against the urging force from the urging unit and the lower roller 502 engages in the sponge roller 501.

Note that when the eccentric cam 505 is rotated by 180°, the amount of engagement of the lower roller 502 into the sponge roller 501 becomes maximum as illustrated in FIG. 5.

That is, in the present exemplary embodiment, the vertical position of the roller shaft 503 is determined by adjusting the rotational angle of the eccentric cam 505. Thus, the amount of engagement of the lower roller 502 into the sponge roller 501 can be changed (adjusted). Furthermore, the curling correction amount (the correction force) can be changed by changing the amount of engagement as described above.

Note that in the example illustrated in FIG. 4, the eccentric cam 505 is positioned at a state before correcting the curling amount. In the present exemplary embodiment, the amount of engagement is changed by driving the eccentric cam 505 by 12° at a time, for example, starting from the position. The upward curling correction roller pair 341 operates in the above-described manner. The downward curling correction roller pair 340 has a configuration substantially similar to that of the upward curling correction roller pair 341 and operates in substantially the same manner except that in the downward curling correction roller pair 340, the sponge roller 501 and the lower roller 502 are provided at the opposite positions in the vertical direction.

Meanwhile, the larger the amount of toner fixed on a sheet is, the greater the amount of curling that may occur as the time passes may become. In this regard, in order to reduce the amount of curling that may occur after a predetermined length of time has elapsed, the present exemplary embodiment outputs a printed sheet after applying reverse curling to the printed sheet if the sheet is curled, by using either one of the upward curling correction roller pair 341 and the downward curling correction roller pair 340. Thus, the present exemplary embodiment can prevent a sheet from being curled after a predetermined length of time has elapsed.

In the present exemplary embodiment, the amount of engagement of the curling correction roller pair can be set at a plurality of levels. Thus, the present exemplary embodiment changes the amount of engagement according to the amount of curling to be corrected. More specifically, the amount of engagement can be controlled at fifteen levels by driving the eccentric cam 505 by 12° at a time. Furthermore, if the amount of engagement is set at the level 15, a maximum reverse curling can be applied to a curled sheet.

Now, an exemplary configuration of the paper feed deck 50 a will be described in detail below with reference to FIG. 6.

The paper feed deck 50 a includes paper feed cassettes 403 through 405. The paper feed deck 50 a feeds a sheet from any one of the paper feed cassettes 403 through 405 according to an instruction from the control unit 201. Hereinbelow, the sheet feeding operation performed by the paper feed deck 50 a will be described in detail below with reference to the cross section of the paper feed deck 50 a illustrated in FIG. 6.

In feeding a sheet from the paper feed cassette 403, of the paper feed cassettes 403 through 405, the control unit 201 picks up a sheet by rotating a paper feed roller 423 and conveys the sheet to an upper vertical path 415. After conveying the sheet into the upper vertical path 415, the control unit 201 then performs control so that the sheet is conveyed into a buffer path 412 via a straight path 413. Then, the sheet is conveyed into the sheet conveyance path of the image forming apparatus 100. After entering the image forming apparatus 100, the sheet is conveyed to the registration roller 316. The operation to be performed thereafter is the same as the operation for feeding a sheet from the paper feed cassette 401. Accordingly, the detailed description thereof will not be repeated here.

In feeding a sheet from the paper feed cassette 404, the control unit 201 picks up a sheet by rotating a paper feed roller 424 and conveys the sheet to a lower vertical path 416. After conveying the sheet into the lower vertical path 416, the control unit 201 then performs control so that the sheet is conveyed into the buffer path 412 via the straight path 413. Then, the sheet is conveyed into the sheet conveyance path of the image forming apparatus 100. After entering the image forming apparatus 100, the sheet is conveyed to the registration roller 316. The operation to be performed thereafter is the same as the operation for feeding a sheet from the paper feed cassette 401. Accordingly, the detailed description thereof will not be repeated here.

In feeding a sheet from the paper feed cassette 405, the control unit 201 picks up a sheet by rotating a paper feed roller 425 and conveys the sheet to the lower vertical path 416 in the above-described manner.

Furthermore, if double feeding of sheets has occurred, the paper feed deck 50 a detects the double feeding state with a double feed detection sensor 417. Here, “double feeding” refers to a state in which a plurality of sheets is fed at the same time in an overlapping state. The double feed detection sensor 417 transmits a signal indicating that the double feeding has occurred to the control unit 201. After receiving the signal, the control unit 201 discharges the double-fed sheet onto an escape tray 411 via an escape path 410.

The paper feed deck 50 b has a configuration similar to that of the paper feed deck 50 a. The paper feed deck 50 b feeds a sheet from any one of paper feed cassettes 406 through 408 according to an instruction from the control unit 201. Then, the paper feed deck 50 b conveys the sheet into an upper vertical path or a lower vertical path. Furthermore, the paper feed deck 50 b conveys the sheet to a cascade path 414 of the paper feed deck 50 a via a straight path and a buffer path.

After having been conveyed to the cascade path 414 of the paper feed deck 50 a, the sheet is conveyed to the buffer path 412 via the straight path 413. Then, the sheet is conveyed to the registration roller 316 via the conveyance path of the image forming apparatus 100. The operation to be performed thereafter is the same as the operation for feeding the sheet from the paper feed cassette 401. Accordingly, the detailed description thereof will not be repeated here.

As described above, the image forming system 1000 can feed a sheet from any one of the paper feed cassettes 401 through 408.

Now, an exemplary configuration of the large-capacity stacker 200 a will be described in detail below with reference to FIG. 7. FIG. 7 is a cross section illustrating an example of a configuration of the large-capacity stacker 200 a according to the present exemplary embodiment.

Referring to FIG. 7, the large-capacity stacker 200 a conveys the sheet that has been conveyed from an upstream apparatus selectively into a straight path 253, an escape path 251, or a stack path 252. The straight path 253 is a conveyance path for transferring the sheet that has been received from an upstream apparatus to a downstream apparatus. The escape path 251 is the conveyance path for conveying the sheet onto an escape tray 257. The escape path 251 is used in executing a verification operation (proof printing) for verifying the finishing state of the printed sheet, for example. The stack path 252 is a conveyance path for discharging the sheet on a stack tray.

Note that a plurality of sensors (not illustrated), which is used to detect a status of conveyance of the sheet and paper jamming, if any, is provided in the sheet conveyance path in the large-capacity stacker 200 a. More specifically, curling amount detection sensors 701 and 702 and a tray full stack state detection sensor 703 are located at positions opposing the surface of the sheets stacked on a stack tray 254.

The control unit 201 receives a signal received from the sensors via a signal line provided between the sheet processing apparatus 200 and the control unit 201 (FIG. 2). The control unit 201 recognizes the conveyance state of the sheet and paper jamming, if any, inside the large-capacity stacker 200 a according to the received signal to control the large-capacity stacker 200 a.

The stack tray 254 is a stacking unit provided on an extendable stay 255. The stack tray 254 stacks the sheets that have been designated to be stacked on the large-capacity stacker 200 a. The control unit 201 discharges and stacks the sheet that has been designated to be discharged on the large-capacity stacker 200 a on the stack tray 254 via the stack path 252. A wagon 256 is provided below the extendable stay 255. If a handle (not illustrated) is mounted on the wagon 256, the user can carry the stacked output product contained thereon to another offline finisher.

The large-capacity stacker 200 a includes a front door as illustrated in FIG. 1. By opening the front door, the user can take out the sheet stacked in the large-capacity stacker 200 a. Furthermore, the large-capacity stacker 200 a includes a sensor for detecting the open/closed state of the front door. The control unit 201 elevates the extendable stay 255 to a position appropriate for stacking the output product when the front door is closed according to a signal from the sensor.

Furthermore, the control unit 201 descends the stack tray 254 by controlling the extendable stay 255 every time a sheet is stacked on the stack tray 254. Thus, the sheet discharged from the stack path 252 can be stacked on the top of the sheet bundle stacked on the stack tray 254. If the stack state detection sensor 703 has detected that the stack tray 254 has been descended to a position of the stack state detection sensor 703, the stack state detection sensor 703 transmits a tray-full signal to the control unit 201. Here, the “tray-full signal” indicates that the number of stacked sheets has reached a predetermined quantity and thus the stack tray 254 is in a fully stacked state.

When the tray-full signal is received from the tray full stack state detection sensor 703, the control unit 201 recognizes that the stack tray 254 is in a fully stacked state. Furthermore, if the front door has been opened by the operator (user) or if the user has instructed to open the front door, the control unit 201 descends the stack tray 254.

The control unit 201 determines the amount of curling of the sheets stacked on the stack tray 254 by using the curling detection sensors 701 and 702. The curling detection sensors 701 and 702 can be moved in the sheet conveyance direction. The control unit 201 moves the curling detection sensor 701 to a position for detecting an edge of the sheet according to the size of the sheet to be printed while moving the curling detection sensor 702 to a position for detecting the center of the sheet. The curling detection sensors 701 and 702 each transmit a detected value to the control unit 201.

The curling detection sensors 701 and 702 each measure and detect the total thickness of the sheet bundle on the stack tray 254 at the corresponding positions of the sheet every time another sheet is stacked on the stack tray 254. Then, the curling detection sensors 701 and 702 each transmit the result of the measurement to the control unit 201.

The control unit 201 determines the amount of curling of the sheet according to the difference between the distances (thickness values) detected by the curling detection sensors 701 and 702. The control unit 201 determines that the sheet is curled (that excessive curling has occurred) if the amount of curling of the sheet is greater than a predetermined curling amount.

FIG. 8 illustrates an exemplary configuration of the saddle stitch binding machine 200 c according to the present exemplary embodiment.

The saddle stitch binding machine 200 c executes stapling processing, cutting processing, punching processing, and folding processing on the sheet that has been conveyed from the image forming apparatus 100.

Note that a plurality of sheet detection sensors for detecting the state of conveyance of the sheet or paper jamming, if any, is provided in the sheet conveyance path in the saddle stitch binding machine 200 c. Each of the sensors transmits detected information to the control unit 201 via a signal line for data communication with the control unit 201 provided between the sheet processing apparatus 200 and the control unit 201 (FIG. 2). The control unit 201 recognizes the conveyance state of the sheet and paper jamming, if any, inside the saddle stitch binding machine 200 c according to the signal received from the saddle stitch binding machine 200 c to control the saddle stitch binding machine 200 c.

If another sheet processing apparatus is provided between the saddle stitch binding machine 200 c and the image forming apparatus 100, the sensors each transmit detected information about the large-capacity stacker to the control unit 201 via a signal line provided to the sheet processing apparatus.

Referring to FIG. 8, the saddle stitch binding machine 200 c includes a sample tray 281, an output tray 282, and a booklet tray 283. The control unit 201 performs control for switching the unit (tray) to be used according to the type of the job and the number of recording sheets to be discharged.

In executing stapling processing, the saddle stitch binding machine 200 c performs control for conveying the sheet that has been transmitted from the large-capacity stacker 200 b onto the output tray 282. The saddle stitch binding machine 200 c serially stacks the sheets on the processing tray 284, which is provided within the saddle stitch binding machine 200 c, and binds the sheet bundle with a stapler 285 on the processing tray 284 before outputting the bound sheets onto the output tray 282.

In addition, the saddle stitch binding machine 200 c includes a z-folding machine 292 and a puncher 286. The z-folding machine 292 folds the sheet in a z-like shape. The puncher 286 provides two (or more) holes on the sheet used for filing the print product. The z-folding machine 292 and the puncher 286 each execute respective processing operations according to the print setting where necessary. The sheet that has been processed as described above is then conveyed through the saddle stitch binding machine 200 c and discharged on the paper discharge tray, such as the output tray 282 or the sample tray 281.

The saddle stitcher unit 287 stacks a plurality of sheets. Furthermore, the saddle stitcher unit 287 folds the sheet bundle in two by causing the center of the sheet bundle to engage the roller after binding the stacked sheet bundle at two positions at the center thereof. Thus, the saddle stitch binding machine 200 c executes the saddle stitching binding processing for generating a bookbound print product, such as a brochure. The sheet bundle bound with the saddle stitcher unit 287 is discharged onto the booklet tray 283.

Furthermore, an inserter 293 is used for conveying the sheet set on an inserter tray 291 to the output tray 282, the sample tray 281, or the saddle stitcher unit 287. Thus, the sheet set on the inserter 293 can be inserted between the sheets to be conveyed from the image forming apparatus 100 into the saddle stitch binding machine 200 c.

Furthermore, the saddle stitch binding machine 200 c includes a cutting unit 288. The bookbound print product discharged from the saddle stitcher unit 287 onto the booklet tray 283 is then conveyed to the cutting unit 288. In this case, the bookbound print product is fed by the roller by a predetermined length. Then, the bookbound print product is cut by a cutter unit 289 by a predetermined length. Then, the cut bookbound print product is stacked on a booklet holding unit 290.

Now, an exemplary configuration of the operation unit 203 will be described in detail below with reference to FIG. 9. FIG. 9 illustrates an exemplary configuration of the operation unit 203 according to the present exemplary embodiment.

Referring to FIG. 9, the operation unit 203 includes a touch panel unit 203 a and a key input unit 203 b. The touch panel unit 203 a is constituted by an LCD and a transparent electrode attached on the LCD. The touch panel 203 a displays various setting screens used for receiving an instruction from the operator.

That is, the touch panel 203 a not only functions to display various setting screens but also functions to input an instruction to receive an instruction from the user. The screen displayed on the touch panel 203 a is displayed by executing a display program previously stored on the ROM 205 with the control unit 201.

The key input unit 203 b includes a power key 901, a start key 903, a stop key 902, a reset key 904, an operator mode key 905, a numeric keypad 906, and a clear key 907. Here, the start key 903 can be operated by the operator to issue an instruction for starting a copy job or a send job by the printing apparatus 100. The numeric keypad 906 can be operated by the operator to enter a numerical value for a print setting item, such as the number of print copies. The clear key 907 can be operated by the operator to clear various parameters set with the numeric keypad 906.

In executing a copy job, the control unit 201 instructs the paper feed cassette on which the sheets of the size and the type that have been set by the user to feed a sheet. The paper feed cassette to which the instruction has been issued then feeds a sheet. Furthermore, it is also useful if the user can directly designate a paper feed cassette instead of designating the size and the type of the sheet. In this case, the control unit 201 instructs the designated paper feed cassette to feed a sheet.

In addition, by operating the operation unit 203, the user can adjust the curling correction amount separately and independently on each paper feed cassette. FIG. 10 illustrates an example of a screen displayed on the operation unit 203 when the user has pressed the user mode key 905.

When a button 3501 is pressed by the user on the screen illustrated in FIG. 10, a screen illustrated in FIG. 11 is displayed on the operation unit 203.

The screen illustrated in FIG. 11 is a screen for selecting the paper feed cassette, of a plurality of paper feed cassettes of the image forming system 1000, whose curling correction amount is to be adjusted with the curling correction roller pairs 340 and 341. Sheet feed unit buttons 1 through 8 respectively correspond to the paper feed cassettes 401 through 408. When the user presses the button corresponding to the paper feed unit whose amount of curling correction is to be adjusted with the curling correction roller pairs 340 and 341, of the paper feed unit buttons 1 through 8, a screen illustrated in FIG. 12 is displayed on the operation unit 203.

The screen illustrated in FIG. 12 is a screen for setting the curling correction amount with respect to the curling correction roller pairs 340 and 341. The user adjusts the curling correction amount by operating a button 3703 (including a “+” (increase) key and a “−” (decrease) key) on the screen illustrated in FIG. 12. In the screen illustrated in FIG. 12, a default value (the curling correction value: “0”) is set.

Suppose here, for example, that the user has pressed the paper feed unit button 1 via the screen illustrated in FIG. 11 and has set a parameter “+10” as the curling correction value by pressing the button 3703 via the screen illustrated in FIG. 12. In this case, the control unit 201 stores the curling correction value “+10” on the RAM 206 in association with the paper feed cassette 401, which corresponds to the paper feed unit button 1.

The control unit 201 rotates the eccentric cam 505 by the amount corresponding to the set curling correction value when the sheet fed from the paper feed cassette 401 is conveyed through the curling correction roller pairs 340 and 341. If a value “+10” is set as the curling correction value, the control unit 201 rotates the eccentric cam 505 (FIG. 5) of the upward curling correction roller pair 341 by 120° (i.e., 12°×10) from a position at which the rotational angle of the eccentric cam 505 is 0° (the state in which the lower roller 502 has not been engaged into the sponge roller 501). At the same time, the control unit 201 performs control so that the amount of engagement of the downward curling correction roller pair 340 into the sponge roller 501 becomes “0”.

On the other hand, suppose here, for example, that the user has operated the button 3703 to set a value “−5” as the curling correction value. In this case, the control unit 201 stores the curling correction value “−5” on the RAM 206 in association with the paper feed cassette 401, which corresponds to the paper feed unit button 1.

The control unit 201 rotates the eccentric cam 505 by the amount corresponding to the set curling correction value when the sheet fed from the paper feed cassette 401 is conveyed through the curling correction roller pairs 340 and 341. If a value “−5” is set as the curling correction value, the control unit 201 rotates the eccentric cam 505 (FIG. 5) of the downward curling correction roller pair 340 by 60° (i.e., 12°33 5) from a position at which the rotational angle of the eccentric cam 505 is 0°. At the same time, the control unit 201 performs control so that the amount of engagement of the upward curling correction roller pair 341 into the sponge roller 501 becomes “0”.

With the above-described configuration, the present exemplary embodiment can allow the user to input a curling correction value for the curling correction roller pairs 340 and 341 separately and differently for each of a plurality of paper feed units of the image forming system 1000.

Now, an exemplary control by the control unit 201 for executing a job according to the first exemplary embodiment of the present invention will be described in detail below. Processing illustrated in the flow chart in FIGS. 13 and 14 is executed with the control unit 201 by loading and executing the program stored on the ROM 205. A job management table illustrated in FIG. 15 is stored on the RAM 206 and used for managing information about a job that has been instructed by the user to be executed.

The job management table manages various information about the received job. The various information managed with the job management table includes a job number, a job name, the status of the job, a paper feed cassette used in the job, or a sheet discharge destination designated in the job. The content of the information is managed by the control unit 201.

Referring to FIG. 13, in step S2501, the control unit 201 determines whether a job to be processed, such as a scan job or a print job, exists. The control unit 201 determines that a job to be processed exists if the user has pressed the start key 903 of the operation unit 203, for example. Furthermore, the control unit 201 determines that a job to be processed exists if the control unit 201 has received a print job from the external I/F unit 209 and if the print job has been stored on a print queue as the data to be printed. If a job to be processed exists in step S2501 (YES in step S2501), then the processing advances to step S2502.

On the other hand, if no job to be processed exists in step S2501 (NO in step S2501), then the processing returns to step S2501 to repeat the processing therein and wait until a job to be processed is received.

In step S2502, the control unit 201 refers to the print setting of the job to be processed. Then, the control unit 201 issues a sheet feeding instruction to the paper feed cassette indicated and specified in the print setting. At this time, the control unit 201 records paper feed cassette information indicating the paper feed cassette to which the sheet feeding instruction has been issued in a “paper feed cassette used” field of the job management table (FIG. 15).

In step S2503, the control unit 201 forms an image on the fed sheet. If the job to be processed is a copy job, then the control unit 201 reads an image of the document with the scanner unit 202 and executes the image forming operation described above with reference to FIG. 3 with the operation unit 203 according to the set print setting.

On the other hand, if the job to be processed is a print job, then the control unit 201 receives image data via the external I/F unit 209 and executes the image forming operation described above with reference to FIG. 3 with the operation unit 203 according to the print setting associated with the image data.

In step S2504, the control unit 201 discharges the sheet having an image formed thereon to the paper discharge unit designated in the print setting. If the user has set the setting so that the sheet is to be discharged to the large-capacity stacker, then the control unit 201 discharges the sheet having an image formed thereon by the image forming apparatus 100 to the large-capacity stacker.

On the other hand, if the user has set the setting so that the sheet is to be discharged to the saddle stitch binding machine 200 c, then the control unit 201 discharges the sheet having an image formed thereon by the image forming apparatus 100 to the saddle stitch binding machine 200 c.

In step S2505, the control unit 201 determines whether a tray full stack state has occurred on the stack tray 254 of the large-capacity stacker according to a tray-full signal transmitted from the tray full stack state detection sensor 703. If it is determined according to the signal from the stack state detection sensor 703 that no tray full stack state has occurred in step S2505 (NO in step S2505), then the control unit 201 suspends the paper feeding operation. Then, the processing advances to step S2506.

On the other hand, if it is determined in step S2505 that a tray full stack state has occurred (YES in step S2505), then the processing advances to step S2601 in FIG. 14, which is continued from FIG. 13 by indicating the continued processing with a continued processing reference numeral “1” indicated with a circle in FIGS. 13 and 14.

In step S2506, the control unit 201 determines whether the printing of designated pages has been completed. If the printing of designated pages has been completed in step S2506 (YES in step S2506), then the processing ends. On the other hand, if the printing of designated pages has not been completed yet, the processing returns to step S2502.

As described above, if it is determined that a tray full stack state has occurred on the stack tray 254 of the large-capacity stacker, then the processing advances to step S2601 in FIG. 14.

In step S2601, the control unit 201 determines whether any sheet has been curled to cause the tray full stack state according to the signal from the curling detection sensors 701 and 702. More specifically, in step S2601, the control unit 201 determines the amount of curling of the sheet according to the signal from the curling detection sensors 701 and 702. If the determined sheet curling amount is greater than a predetermined sheet curling amount, then the control unit 201 determines that the curling of the sheet has caused the tray full stack state. If it is determined in step S2601 that the curling of the sheet has caused the tray full stack state (YES in step S2601), then the processing advances to step S2602. In step S2602, the control unit 201 determines whether any job is currently being executed.

If it is determined that no job is currently being executed in step S2602 (NO in step S2602), then the processing advances to step S2603. In step S2603, the control unit 201 displays a message (FIG. 18) on the operation unit 203 indicating that the stack tray 254 is in a tray full stack state (i.e., that the stack tray 254 is full of or almost full of sheets stacked thereon). In this regard, it is also useful if the control unit 201 displays a message indicating that the curling of the sheet has caused the tray full stack state on the operation unit 203. With this configuration, the present exemplary embodiment can allow the user to clearly distinguish between the causes for the tray full stack state.

On the other hand, if a job is currently being executed in step S2602 (YES in step S2602), then the processing advances to step S2604. In step S2604, the control unit 201 specifies (identifies) the paper feed cassette used in the current job according to the job management table illustrated in FIG. 15.

In step S2605, the control unit 201 displays a message illustrated in FIG. 16 on the operation unit 203 to prompt the user to enter a curling correction value for the paper feed cassette specified in step S2604.

If the user presses a curling correction button 3903 via the screen illustrated in FIG. 16, then a screen illustrated in FIG. 17 is displayed on the operation unit 203. The control unit 201 performs control so that the color of a button 3601, which corresponds to the paper feed cassette specified in step S2604, is displayed in a color different from those of the other paper feed unit buttons. Accordingly, the user can easily recognize the paper feed cassette whose curling of the sheet is to be corrected.

Referring to FIG. 17, when the button 3601 is selected and the setting button 3602 is pressed by the user, the control unit 201 displays the screen illustrated in FIG. 12 on the operation unit 203. The user can adjust the curling correction amount for the paper feed cassette 401 corresponding to the paper feed unit button 3601 via the screen illustrated in FIG. 12. If an OK button illustrated in FIG. 12 is pressed by the user and a “resume printing” button 3902 illustrated in FIG. 16 is pressed by the user, then the processing advances to step S2606 (FIG. 14) and the control unit 201 resumes printing.

In step S2606, the control unit 201 determines whether the tray full stack state of the stack tray 254 has been solved. If a tray-full signal is no longer transmitted from the stack state detection sensor 703, then the control unit 201 determines that the tray full stack state has been solved. If it is determined in step S2606 that the tray full stack state has been solved (YES in step S2606), then the processing advances to step S2506 (FIG. 13), which is continued from the processing illustrated in FIG. 14 and indicated with a processing continuation reference numeral “2” indicated with a circle in FIGS. 14 and 13.

Note that in step S2605, the control unit 201 suspends resuming the printing until the “resume printing” button 3902 is pressed by the user, as described above. However, the present invention is not limited to this. That is, it is also useful if the processing advances to step S2606 instead of waiting for the button 3902 to be pressed and the control unit 201 continues the printing by automatically advancing the processing to step S2506 in FIG. 13 if it is determined that the tray full stack state has been solved.

In this case, it is also useful if the control unit 201 executes the processing in step S2606 and beyond while displaying the screen illustrated in FIG. 16, FIG. 17, or FIG. 12 on the operation unit 203. With the above-described configuration, the present exemplary embodiment can increase the efficiency in processing a job by resuming the execution of a suspended job if the tray full stack state has been solved even while the user has been executing an operation for entering a curling correction value.

Furthermore, if the user has changed the curling correction value while executing the job after the execution of the job is resumed, then the control unit 201 performs control for changing the amount of engagement of the curling correction roller pairs 340 and 341 at a timing before the sheet passes through the curling correction roller pairs 340 and 341. With the above-described configuration, the present exemplary embodiment can appropriately correct the curling of a sheet even if the user has changed the setting of the amount of engagement of the curling correction roller pairs 340 and 341 while the sheet is currently being conveyed through the curling correction roller pairs 340 and 341.

On the other hand, if it is determined in step S2601 that no curling of the sheet that may have caused the tray full stack state has occurred (NO in step S2601), then the processing advances to step S2607. In step S2607, the control unit 201 displays a message to prompt the user to remove the sheet from the large-capacity stacker.

In step S2606, the control unit 201 determines whether the full-stack on tray has been solved. If it is determined in step S2606 that the full-stack on tray has been solved (YES in step S2606), then the processing advances to step S2506 (FIG. 13), which is continued from the processing in step S2606 in FIG. 14 (indicated with processing continuation reference numeral “2” indicated with a circle in FIGS. 14 and 13).

As described above with reference to FIGS. 13 and 14, the control unit 201 performs control in executing a job. Now, the present exemplary embodiment will be described in detail below with reference to FIG. 19. Suppose here that sheets fed from a paper feed cassette A have been discharged on the stack tray 254 of the large-capacity stacker 200 a and that the control unit 201 has received a tray-full signal from the stack tray 254 when the sheets fed from the paper feed cassette A have been discharged on the stack tray 254. In this case, the control unit 201 specifies the paper feed unit used in the currently executed job by referring to the job management table illustrated in FIG. 15 and then displays the screen illustrated in FIG. 17.

The screen illustrated in FIG. 17 is displayed when the paper feed cassette A (FIG. 19) is the paper feed cassette 401. By referring to the information displayed on the screen illustrated in FIG. 17, the user can easily recognize the paper feed cassette, of the plurality of paper feed cassettes, which has fed the curled sheet.

The image forming apparatus 100 having the above-described configuration according to the present exemplary embodiment performs the following control with the control unit 201 if a tray full stack state has occurred on the stack tray 254 of the large-capacity stacker and the curling of the sheet has caused the tray full stack state. That is, the control unit 201 displays a screen displaying the paper feed unit that is the paper feed source of the sheet in the currently executed job on the operation unit 203. By referring to the screen, the user can easily recognize the paper feed unit, of the plurality of paper feed units, which has fed the curled sheet.

Furthermore, when the user has selected the paper feed cassette whose curling correction amount is to be adjusted via the screen illustrated in FIG. 17, the image forming apparatus 100 according to the present exemplary embodiment displays the screen illustrated in FIG. 12 to allow the user to adjust the curling correction amount for the paper feed unit. Thus, the user is allowed to adjust the curling correction amount by displaying the screen for adjusting the curling correction amount with a simple operation without shifting the screen displayed on the operation unit 203 from the top (default) screen to the screen for correcting the curling of the sheet that displays the paper feed unit.

In the present exemplary embodiment, in step S2605, the control unit 201 displays the notification screens illustrated in FIGS. 16 and 17. However, the present invention is not limited to this. That is, it is also useful if the control unit 201 displays the screen illustrated in FIG. 18 in step S2605. In this case, the time required for the user to adjust the curling correction amount can be reduced.

In the present exemplary embodiment, in step S2505, the control unit 201 determines whether curling of the sheet has occurred if it is determined that the tray full stack state has occurred on the stack tray 254 of the large-capacity stacker. However, the present invention is not limited to this. That is, it is also useful if the control unit 201 determines whether curling of the sheet discharged on the stack tray 254 has occurred even if the tray full stack state has not occurred.

In this regard, it is also useful, for example, if the control unit 201 determines whether curling of the discharged sheet has occurred with the curling detection sensors 701 and 702 every time a sheet is discharged on the stack tray 254. In this case, the control unit 201 can refer to the job management table to specify the paper feed unit that has fed the curled sheet and notify the curled sheet feeding source paper feed unit to the user. With this configuration, the present exemplary embodiment can allow the user to easily recognize the paper feed unit that has fed the curled sheet even if a tray full stack state has not occurred.

Now, a second exemplary embodiment of the present invention will be described in detail below.

In the first exemplary embodiment, if a tray full stack state has occurred on the stack tray 254 of the large-capacity stacker and the curling of the sheet has caused the tray full stack state as illustrated in FIG. 19, the control unit 201 displays the screen displaying one paper feed cassette that is the paper feed source of the sheet in the currently executed job. In this regard, the number of paper feed sources in the currently executed job may not be limited to one. That is, a plurality of paper feed units may feed sheets in the currently executed job. That is, a plurality of paper feed source units may be used in a job in which the user has instructed to feed sheets from a plurality of paper feed cassettes or in a job in which the paper feed cassette (paper feed source unit) has been switched because the quantity of sheets remaining in the paper feed unit has become small during executing the job.

The second exemplary embodiment concerns control executed when the sheets used in the currently executed job has been fed from a plurality of different paper feed sources in the above-described case, for example.

Main components of the image forming system 1000 according to the second exemplary embodiment are similar to those of the image forming system 1000 of the first exemplary embodiment. Accordingly, the detailed description thereof will not be repeated here. That is, only units and components different from those of the first exemplary embodiment will be described in detail below.

FIG. 20 illustrates a job management table stored on the RAM 206 in the present exemplary embodiment. Referring to FIG. 20, in executing a job B, a plurality of paper feed cassettes is used.

In specifying the paper feed unit whose curling of the sheet is to be corrected in step S2604 (FIG. 14), the control unit 201 refers to a job management table illustrated in FIG. 20 to specify the paper feed unit used in the currently executed job. The job management table illustrated in FIG. 20 stores information indicating that a plurality of paper feed cassettes (the paper feed cassettes 401 and 404) has been used during the currently executed job B.

After specifying the paper feed cassette on which the curling correction amount is to be adjusted in step S2604, the control unit 201 displays the screen illustrated in FIG. 16 on the operation unit 203. When the user presses the curling correction button 3903 via the screen illustrated in FIG. 16, the control unit 201 displays a screen illustrated in FIG. 21 on the operation unit 203.

Paper feed unit buttons 1 through 8 (FIG. 21) correspond to the paper feed cassettes 401 through 408, respectively. On the screen illustrated in FIG. 21, the control unit 201 performs control so that the paper feed unit buttons 1 (a button 4001 in FIG. 21) and 4 (a button 4002 in FIG. 21) are displayed in a color different from the color of the other paper feed unit buttons to indicate the paper feed units whose curling of the sheet is to be corrected. With this configuration, the present exemplary embodiment can allow the user to easily recognize the paper feed units whose curling of the sheet is to be corrected.

When the user presses the setting button 4003 in the state where the paper feed unit button 1 has been selected, the control unit 201 displays a screen illustrated in FIG. 22 on the operation unit 203. The user can adjust the curling correction amount via the screen illustrated in FIG. 22 by operating a button 3705 for the paper feed cassette 401, which corresponds to paper feed unit button 1.

The screen illustrated in FIG. 22 includes a “next” button 3704. By operating the “next” button 3704, the user can adjust the curling correction amount for a plurality of paper feed cassettes. Furthermore, by pressing the “next” button 3704, the user can shift the screen to a screen for adjusting the curling correction amount for another paper feed unit.

In the present exemplary embodiment, when the user presses the “next” button 3704 via the screen illustrated in FIG. 22, a screen for adjusting the curling correction amount for the paper feed cassette 404 is displayed.

The processing in step S2604 and beyond is similar to that described above in the first exemplary embodiment. Accordingly, the detailed description thereof will not be repeated here.

In the present exemplary embodiment, the control unit 201 performs the above-described control. Now, the present exemplary embodiment will be described in detail below with reference to FIG. 23.

Suppose here that sheets fed from a paper feed cassette A have been discharged on the stack tray 254 of the large-capacity stacker 200 a and then a sheet fed from a paper feed cassette B has been discharged on the same stack tray as illustrated in FIG. 23. If the control unit 201 has received a tray-full signal from the stack tray while the sheet is being fed from the paper feed cassette B, then the control unit 201 specifies the paper feed unit used in the currently executed job by referring to the job management table illustrated in FIG. 19 and then displays the screen illustrated in FIG. 21.

The screen illustrated in FIG. 21 is displayed when the paper feed cassette A is the paper feed cassette 401 and the paper feed cassette B is the paper feed cassette 404 or vice versa. By referring to the information displayed on the screen illustrated in FIG. 21, the user can easily recognize the specific paper feed cassettes, of the plurality of paper feed cassettes, which have fed the curled sheets.

The image forming apparatus 100 having the above-described configuration according to the present exemplary embodiment performs the following control with the control unit 201 if a tray full stack state has occurred on the stack tray 254 of the large-capacity stacker and the curling of the sheet has caused the tray full stack state. That is, the control unit 201 displays a screen displaying a plurality of paper feed units that are the paper feed sources of the sheets in the currently executed job on the operation unit 203. By referring to the screen, the user can easily recognize the paper feed source unit, of the plurality of paper feed units, that has fed the curled sheet even when a plurality of paper feed units whose curling of the sheet is to be corrected exists. Furthermore, the present exemplary embodiment can allow the user to easily adjust the curling correction amount for the paper feed units that have fed the curled sheets.

Furthermore, when the user has selected the paper feed cassette whose curling correction amount is to be adjusted via the screen illustrated in FIG. 21, the image forming apparatus 100 according to the present exemplary embodiment displays the screen illustrated in FIG. 22 to allow the user to adjust the curling correction amount for the paper feed unit. Thus, the user is allowed to adjust the curling correction amount by displaying the screen for adjusting the curling correction amount with a simple operation without shifting the screen displayed on the operation unit 203 from the top (default) screen to the screen for correcting the curling of the sheet that displays the paper feed unit.

Now, a third exemplary embodiment of the present invention will be described in detail below.

In the second exemplary embodiment, if a tray full stack state has occurred on the stack tray 254 of the large-capacity stacker and the curling of the sheet has caused the tray full stack state as illustrated in FIG. 23, the control unit 201 displays the screen displaying a plurality of paper feed cassettes that are the paper feed sources of the sheets in the currently executed job. In this regard, the sheets that have been discharged and stacked on the stack tray 254 may not be limited to those in the currently executed job. That is, sheets discharged in another job that has been completed may be stacked on the same stack tray. The third exemplary embodiment concerns control executed when sheets that have been discharged in another completed job are stacked on the stack tray.

Main components of the image forming system 1000 according to the third exemplary embodiment are similar to those of the image forming system 1000 of the second exemplary embodiment. Accordingly, the detailed description thereof will not be repeated here. That is, only units and components different from those of the second exemplary embodiment will be described in detail below.

FIG. 24 illustrates a job management table stored on the RAM 206 in the present exemplary embodiment. Referring to FIG. 24, a job A has been already completed. The paper discharge destination is the stack tray 254 of the large-capacity stacker 200 a in the job A. Furthermore, a “removal flag” stored in the job management table illustrated in FIG. 24 indicates that the sheets discharged by executing the job A have not been removed from the stack tray.

When the sheets are removed therefrom, the control unit 201 changes the parameter for the removal flag to “removed”. If it is detected that the sheets on the stack tray have been removed according to a signal from a sheet presence detection sensor (not illustrated) of the large-capacity stacker, then the control unit 201 recognizes that the sheets have been removed. In this case, the control unit 201 changes the parameter for the removal flag from “unremoved” to “removed”.

If the parameter “unremoved” has been set for a plurality of removal flags and the sheets are removed in this state, the control unit 201 changes the parameters for all the removal flags from “unremoved” to “removed”. In this regard, it is also useful if the control unit 201 changes the parameters for the removal flag from “unremoved” to “removed” if a signal indicating that the front door of the large-capacity stacker has been opened is received from the door open/closed state sensor of the large-capacity stacker.

FIG. 25 is a flow chart illustrating processing executed by the control unit 201 according to the present exemplary embodiment. The processing illustrated in the flow chart in FIG. 25 is executed by the control unit 201 loading and executing a program from the ROM 205.

Note that the control unit 201 executes the processing illustrated in the flow chart in FIG. 25 if a tray full stack state has occurred in step S2505 in FIG. 13 during processing illustrated in FIG. 13.

Referring to FIG. 25, in step S2611, the control unit 201 determines whether curling of the sheet has occurred and the curling of the sheet has caused a tray full stack state according to a signal from the curling detection sensors 701 and 702. If the curling of the sheet has caused the tray full stack state in step S2611 (YES in step S2611), then the processing advances to step S2612. In step S2612, the control unit 201 determines whether any job is currently being being executed.

If it is determined that no job is currently being executed in step S2612 (NO in step S2612), then the processing advances to step S2613. In step S2613, the control unit 201 specifies (identifies) the paper feed cassette used in the completed job. In step S2614, the control unit 201 displays a message on the operation unit 203 indicating that the stack tray 254 is in a tray full stack state (i.e., that the stack tray 254 is full of or almost full of sheets stacked thereon) At the same time, the control unit 201 displays the screen illustrated in FIG. 16 on the operation unit 203.

When the user presses the button 3903 on the screen illustrated in FIG. 16, the control unit 201 displays a screen on the operation unit 203 that displays the paper feed unit button corresponding to the paper feed cassette specified in step S2614 in a color different from the colors of the other paper feed unit buttons.

On the other hand, if a job is currently being executed in step S2612 (YES in step S2612), then the processing advances to step S2615. In step S2615, the control unit 201 performs control illustrated in FIG. 26. FIG. 26 illustrates exemplary control according to the present exemplary embodiment.

Referring to FIG. 26, in step S2621, the control unit 201 determines whether any completed job whose removal flag has the parameter “unremoved” exists. If a completed job whose removal flag has the parameter “unremoved” exists (YES in step S2621), then the processing advances to step S2622. In step S2622, the control unit 201 refers to the job management table illustrated in FIG. 24 to specify (identify) the paper feed cassette used in the completed job and the currently executed job. Then, the processing advances to step S2616 in FIG. 25.

In step S2616, the control unit 201 changes the color of the paper feed unit button corresponding to the paper feed cassette specified in step S2622 and displays the button on the operation unit 203. In this regard, FIG. 27 illustrates an example of the screen displayed on the operation unit 203 in step S2616.

On the other hand, if no completed job exists in step S2621 (NO in step S2621), then the processing advances to step S2623. In step S2623, the control unit 201 refers to the job management table to specify (identify) the paper feed cassette used in the currently executed job. Then, the processing advances to step S2616 in FIG. 25.

The processing performed in step S2616 and beyond is similar to that of the second exemplary embodiment. For example, steps S2606 and S2607 of FIG. 14 correspond to steps S2617 and S2618 of FIG. 25, respectively. Accordingly, the detailed description thereof will not be repeated here.

The image forming apparatus 100 having the above-described configuration according to the present exemplary embodiment performs the following control with the control unit 201 if a tray full stack state has occurred on the stack tray 254 of the large-capacity stacker 200 a and the curling of the sheet has caused the tray full stack state.

That is, the control unit 201 determines whether any completed job whose sheets discharged on the stack tray 254 of the large-capacity stacker have not been removed from the stack tray 254 exists. If a completed job satisfying the above-described condition exists, the control unit 201 specifies the paper feed cassette used in the completed job as well as the paper feed cassette used in the currently executed job. Furthermore, the control unit 201 displays the specified paper feed cassette on the operation unit 203 as the paper feed cassette whose curling correction amount is to be adjusted. With the above-described configuration, the present exemplary embodiment can allow the user to easily recognize the paper feed cassette whose curling of the sheet is to be corrected with respect to the completed job as well as the currently executed job.

Suppose here that in a completed job, sheets fed from a paper feed cassette A have been discharged on the stack tray 254 of the large-capacity stacker 200 b and then sheets fed from a paper feed cassette B have been discharged on the same stack tray as illustrated in FIG. 28. If the control unit 201 has received a tray-full signal from the stack tray while the sheet is being fed from a paper feed cassette D after discharging sheets from a paper feed cassette C, then the control unit 201 specifies the paper feed unit used in the currently executed job by referring to the job management table illustrated in FIG. 24 and then displays the screen illustrated in FIG. 27.

The screen as illustrated in FIG. 27 is displayed when the paper feed cassette A (FIG. 28) is the paper feed cassette 401, the paper feed cassette B (FIG. 28) is the paper feed cassette 404, the paper feed cassette C (FIG. 28) is the paper feed cassette 403, and the paper feed cassette D (FIG. 28) is the paper feed cassette 405.

The image forming apparatus 100 according to the present exemplary embodiment allows the user to adjust the curling correction amount for the paper feed cassette by selecting the paper feed cassette and pressing a setting button 4102 via the screen illustrated in FIG. 27. Thus, the user is allowed to adjust the curling correction amount by displaying the screen for adjusting the curling correction amount with a simple operation without shifting the screen displayed on the operation unit 203 from the top (default) screen to the screen for correcting the curling of the sheet that displays the paper feed unit.

Now, a fourth exemplary embodiment of the present invention will be described in detail below.

In the above-described third exemplary embodiment, if a tray full stack state has occurred on the stack tray 254 of the large-capacity stacker and the curling of the sheet has caused the tray full stack state as illustrated in FIG. 28, the control unit 201 displays the screen displaying a plurality of paper feed cassettes that are the paper feed sources of sheets in the completed job and the currently executed job. The present exemplary embodiment concerns processing for determining the priority of level of curling correction and notifies the result of the determination to the user if a plurality of paper feed units whose curling of the sheet is to be corrected exists. In the present exemplary embodiment, the priority is determined by the control unit 201 according to the descending numeric order of the number of sheets fed from the paper feed unit.

FIG. 29 illustrates a job management table stored on the RAM 206 according to the present exemplary embodiment. Referring to FIG. 29, a job A is the completed job whose paper discharge destination is the stack tray 254 of the large-capacity stacker 200 a. Furthermore, a “removal flag” stored in the job management table illustrated in FIG. 29 indicates that the sheets discharged by executing the job A have not been removed from the stack tray.

The method for managing the “removal flag” is the same as that in the third exemplary embodiment. Accordingly, the detailed description thereof will not be repeated here. The job management table illustrated in FIG. 29 stores information about the number of sheets that have been fed with respect to each paper feed cassette used in the job. The control unit 201 stores, in the job management table illustrated in FIG. 29, a count value about the number of sheets that have been fed from each paper feed unit by using a counter (not illustrated) according to a signal from a sensor provided at a paper feed port of each paper feed unit.

Main components of and control executed by the image forming system 1000 according to the fourth exemplary embodiment are similar to those in the third exemplary embodiment. Accordingly, the detailed description thereof will not be repeated here. Hereinbelow, only the configuration different from that of the third exemplary embodiment will be described in detail.

The control unit 201 reads the number of sheets fed from each paper feed unit specified in step S2615 (in FIG. 25) and compares the read the numbers of sheets. In step S2616, the control unit 201 determines the priority in the descending numeric order of the number of sheets according to the comparison result. As illustrated in the job management table (FIG. 29), the number of fed sheets is greater in the order of the paper feed cassette 405, the paper feed cassette 403, the paper feed cassette 401, and the paper feed cassette 404, which are used in the job. Accordingly, in step S2616, the control unit 201 displays a screen illustrated in FIG. 30.

The processing in step S2616 and beyond is similar to that in the third exemplary embodiment. Accordingly, the detailed description thereof will not be repeated here.

The image forming apparatus 100 having the above-described configuration according to the present exemplary embodiment performs the following control with the control unit 201 if a tray full stack state has occurred on the stack tray 254 of the large-capacity stacker 200 a and the curling of the sheet has caused the tray full stack state.

That is, the control unit 201 determines whether any completed job whose sheets discharged on the stack tray 254 of the large-capacity stacker have not been removed from the stack tray 254 exists. If a completed job satisfying the above-described condition exists, the control unit 201 specifies the paper feed cassette used in the completed job as well as the paper feed cassette used in the currently executed job. Furthermore, the control unit 201 displays, on the operation unit 203, the screen displaying the plurality of paper feed units that are the sheet feeding source units in the currently executed job and the completed job in the priority of descending numeric order of the number of sheets fed from the paper feed unit whose curling of the sheet is to be corrected. Thus, the present exemplary embodiment can allow the user to easily recognize the paper feed units that are the sources of feeding the sheet whose curling is to be corrected in the descending order of the sheets that have been fed therefrom.

In this regard, suppose here, for example, as illustrated in FIG. 31, that after discharging N sheets (N is an integer of 1 or greater) fed from a paper feed cassette A on the stack tray 254 of the large-capacity stacker 200 a, M sheets (M is an integer of 1 or greater) fed from a paper feed cassette B have been discharged and stacked on the same stack tray. If the control unit 201 has received a tray-full signal from the stack tray in this state while I sheets (I is an integer of 1 or greater) are being fed from a paper feed cassette D after feeding K sheets (K is an integer of 1 or greater) from a paper feed cassette C, then the control unit 201 specifies the paper feed units used in the completed job and the currently executed job by referring to the job management table illustrated in FIG. 29. Furthermore, the control unit 201 compares the number of sheets fed from each of the paper feed cassettes according to the job management table illustrated in FIG. 29. Then, the control unit 201 displays the screen illustrated in FIG. 30.

Here, in the screen illustrated in FIG. 30, the paper feed cassettes are provided with specific ascending numbers starting from “1” in the descending numeric order of the number of sheets fed therefrom. The screen illustrated in FIG. 30 is displayed when the paper feed cassette A is the paper feed cassette 401, the paper feed cassette B is the paper feed cassette 404, the paper feed cassette C is the paper feed cassette 403, and the paper feed cassette D is the paper feed cassette 405.

Furthermore, if it is detected that the user has pressed a setting button 4302 via the screen illustrated in FIG. 30 in a state where the paper feed unit buttons 1, 3, 4, and 5 are selected, then the control unit 201 displays the screen illustrated in FIG. 22 on the operation unit 203. When the user presses the “next” button 3704, the control unit 201 shifts the screens in the order illustrated in FIG. 32 according to the priority (descending numeric order of the number of sheets fed from the paper feed units).

With the above-described configuration, the present exemplary embodiment can allow the user to recognize the paper feed cassettes whose curling of the sheet is to be corrected in the descending numeric order of the number of sheets fed therefrom. In addition, according to the present exemplary embodiment, the user can adjust the curling correction amount for the paper feed units whose curling of the sheet is to be corrected according to the priority determined in the above-described manner.

In the above-described embodiments, the image forming apparatus 100 is connected to the paper feed deck 50 and the control unit 201 displays the paper feed units whose curling of the sheet is to be corrected, which have been specified from among the plurality of paper feed units of the image forming apparatus 100 and the paper feed deck 50, on the operation unit 203. However, the present invention is not limited to this. That is, the paper feed deck 50 is not always necessary. In this regard, if no paper feed deck 50 is provided (if no paper feed deck 50 is connected to the image forming apparatus 100), then it is useful if the control unit 201 displays the paper feed cassette whose curling of the sheet is to be corrected on the operation unit 203, which has been specified from among a plurality of paper feed cassettes of the image forming apparatus 100.

Furthermore, the number of paper feed cassettes of the image forming apparatus 100 and the paper feed deck 50 is not limited to the above-described number. That is, it is also useful if a greater number of paper feed cassettes are provided. Furthermore, it is also useful if the paper feed unit is not a paper feed cassette but a paper feed unit of any other appropriate type.

In the present exemplary embodiment, two paper feed decks 50 (the paper feed decks 50 a and 50 b) are connected to the image forming apparatus 100. However, the present invention is not limited to this. That is, 0 through n (n is a natural number) paper feed decks 50 can be arbitrarily provided and connected to the image forming apparatus 100. Furthermore, The number of large-capacity stackers is not limited to two. That is, 1 through n (n is an integer of 2 or greater) large-capacity stackers can be used.

Furthermore, in the above-described embodiments, the control unit 201 detects the tray full stack state or the occurrence of curling of the sheet, if any, with respect to the sheets stacked on the stack tray 254 of the large-capacity stacker 200 a. The control unit 201 notifies the paper feed unit whose curling of the sheet is to be corrected. However, the above-described control can be performed on the sheets stacked on the stack tray 254 of the large-capacity stacker 200 b or on a paper discharge tray such as the output tray 282 of the saddle stitch binding machine 200 c.

Furthermore, when the tray full stack state has occurred on the stack tray 254 of one large-capacity stacker but the stack tray of another large-capacity stacker can stack the sheet, it is also useful if the control unit 201 performs control for discharging the sheet on the stack tray of the another large-capacity stacker. With this configuration, the present exemplary embodiment can prevent suspension of a currently executed job due to the occurrence of a tray full stack state.

In addition, in the above-described embodiments, various display screens (i.e., the screens illustrated in FIGS. 10 through 12 and FIGS. 16 through 18, for example) are displayed on the operation unit 203 to notify information to the user. However, the notification method is not limited to the method for displaying the button for the specified paper feed unit in a color different from the color of the buttons for the other paper feed units. That is, any method capable of specifying the paper feed unit that has fed the curled sheet can be used.

In addition, the notification to the user can be performed by transmitting information to an external computer (a client computer or a server computer) connected to the image forming apparatus 100 via the external I/F unit 209 and displaying a screen similar to the above-described screen on a display of the external computer. Furthermore, the notification can be performed by a method other than displaying information. That is, it is also useful if the image forming apparatus 100 or an external computer having an audio output unit notifies information to the user by audio information output from the audio output unit.

Furthermore, in the above-described embodiments, an image forming apparatus that forms an image by electrophotographic processing is described as an example of the sheet conveyance apparatus. However, the present invention is not limited to this. That is, the present exemplary embodiment can be implemented on an image forming apparatus that forms an image by an inkjet image forming method. In addition, the present exemplary embodiment can be implemented on an apparatus that does not form an image but corrects the curling of a sheet to be conveyed therethrough.

Moreover, in the above-described embodiments, the user enters a curling correction value for a specific paper feed unit to correct the curling of the sheet. However, various other methods, such as changing the sheet or the image forming condition can be used to address curling of the sheet.

As described above, embodiments of the present invention specify the paper feed unit (s) that has fed the curled sheet and notify the specified paper feed unit(s) to the user. Accordingly, the present exemplary embodiment can allow the user to perform correction of the curling of the sheet separately and independently for each paper feed unit.

Accordingly, the present exemplary embodiment can prevent the degradation of the quality of a resulting processed product. In addition, the present exemplary embodiment can prevent the reduction of the maximum stackable number of sheets on the stack tray due to the curling of the sheet. Furthermore, the present exemplary embodiment can prevent the deterioration of the stability of the sheet bundle stacked on the stack tray, which may otherwise occur due to the curling of the sheet.

Hereinbelow, the configuration of a data processing program that can be read by a sheet processing apparatus according to an exemplary embodiment of the present invention will be described in detail with reference to memory maps illustrated in FIG. 33.

FIG. 33 illustrates a memory map of a computer-readable storage medium that stores various data processing programs that can be read by a sheet processing apparatus according to an exemplary embodiment of the present invention.

Although not illustrated in FIG. 33, information for managing the programs stored in the computer-readable storage medium such as version information and information concerning the creator of a program, for example, can be stored in the computer-readable storage medium. In addition, information that depends on an operating system (OS) of an apparatus that reads the program, such as an icon for specifying and displaying the program, can be stored in the computer-readable storage medium.

In addition, data that is subordinate to the various programs is also managed in a directory of the computer-readable storage medium. In addition, a program for installing the various programs on a computer can be stored in the computer-readable storage medium. In addition, in the case where a program to be installed is compressed, a program for decompressing the compressed program can be stored in the computer-readable storage medium.

In addition, the functions according to the above-described exemplary embodiments can be implemented by a host computer using a program that is externally installed. In this case, the present invention is applied to the case where a group of information including a program is supplied to an output device from a computer-readable storage medium such as a compact disc-read only memory (CD-ROM), a flash memory, and a floppy disk (FD) or from an external computer-readable storage medium through a network.

The present invention can also be achieved by providing a system or an apparatus with a computer-readable storage medium storing program code of software implementing the functions of the embodiments and by reading and executing the program code stored in the computer-readable storage medium with a computer of the system or the apparatus (a central processing unit (CPU) or a micro processing unit (MPU)).

In this case, the program code itself, which is read from the computer-readable storage medium, implements the functions of the embodiments described above, and accordingly, the computer-readable storage medium storing the program code constitutes the present invention. Accordingly, the program can be configured in any form, such as object code, a program executed by an interpreter, and script data supplied to an OS.

As the computer-readable storage medium for supplying such program code, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a magnetooptic disk (MO), a CD-ROM, a compact disc recordable (CD-R), a compact disc rewritable (CD-RW), a magnetic tape, a nonvolatile memory card, a read only memory (ROM), and a digital versatile disc (DVD (DVD-recordable (DVD-R), DVD-rewritable (DVD-RW))), for example, can be used.

In this case, the program code itself, which is read from the computer-readable storage medium, implements the function of the embodiments mentioned above, and accordingly, the computer-readable storage medium storing the program code constitutes the present invention.

The above program can also be supplied by connecting to a web site on the Internet by using a browser of a client computer and by downloading the program from the web site to a computer-readable storage medium such as a hard disk. In addition, the above program can also be supplied by downloading a compressed file that includes an automatic installation function from the web site to a computer-readable storage medium such as a hard disk. The functions of the above embodiments can also be implemented by dividing the program code into a plurality of files and downloading each divided file from different web sites. That is, a World Wide Web (WWW) server and a file transfer protocol (ftp) server for allowing a plurality of users to download the program file for implementing the functional processing configure the present invention.

In addition, the above program can also be supplied by distributing a computer-readable storage medium such as a CD-ROM and the like which stores the program according to the present invention after an encryption thereof, by allowing the user who is qualified for a prescribed condition to download key information for decoding the encryption from the web site via the Internet, and by executing and installing in the computer the encrypted program code by using the key information.

In addition, the functions according to the embodiments described above can be implemented not only by executing the program code read by the computer, but also implemented by the processing in which an OS or the like carries out a part of or the whole of the actual processing based on an instruction given by the program code.

Further, in another aspect of the embodiment of the present invention, after the program code read from the computer-readable storage medium is written in a memory provided in a function expansion board inserted in a computer or a function expansion unit connected to the computer, a CPU and the like provided in the function expansion board or the function expansion unit carries out a part of or the whole of the processing to implement the functions of the embodiments described above.

In the above-described embodiments of the present invention, the control unit 201 of the image forming apparatus 100 primarily performs the above-described various control operations. However, a part of or the entire various control operations can be performed by an external controller provided in an apparatus or a device other than the image forming apparatus 100.

While the present invention has been described with reference to exemplary embodiments is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures, and functions.

This application claims priority from Japanese Patent Application No. 2008-050127 filed Feb. 29, 2008, which is hereby incorporated by reference herein in its entirety. 

1. A sheet processing apparatus configured to convey a sheet fed from any one of a plurality of sheet feed units, the sheet processing apparatus comprising: a curl detecting unit configured to detect curling of the sheet fed from any one of the plurality of sheet feed units; and a specifying unit configured to specify a sheet feed unit that has fed the sheet having the curling detected by the curl detecting unit from among the plurality of sheet feed units.
 2. The sheet processing apparatus according to claim 1, further comprising a notifying unit configured to notify a user of the sheet feed unit specified by the specifying unit.
 3. The sheet processing apparatus according to claim 2, further comprising a sheet output unit configured to discharge the sheet fed from any one of the plurality of sheet feed units to a sheet discharge unit, wherein the specifying unit is configured to, if the curl detecting unit has detected the curling of the sheet, specify the sheet feed unit that has fed the sheet having the detected curling and a sheet feed unit that has fed the sheet existing in the sheet discharge unit, and wherein the notifying unit is configured to notify the user of the sheet feed unit specified by the specifying unit.
 4. The sheet processing apparatus according to claim 3, further comprising a determining unit configured to determine whether a stacking amount of sheets existing in the sheet discharge unit has reached a predetermined value, wherein the notifying unit is configured to, if it is determined by the determining unit that the stacking amount of sheets existing in the sheet discharge unit has reached the predetermined value and the curling of the sheet has been detected by the curl detecting unit, notify the user of the sheet feed unit specified by the specifying unit.
 5. The sheet processing apparatus according to claim 1, further comprising: an input unit configured to input a curling correction amount for correcting the curling of the sheet; and a curl adjustment unit configured to correct the curling of a sheet fed from the sheet feed unit specified by the specifying unit according to the curling correction amount input by the input unit.
 6. The sheet processing apparatus according to claim 5, wherein the input unit is configured to input the curling correction amount with respect to each sheet feed unit of the plurality of sheet feed units, and wherein the curl adjustment unit is configured to correct the curling of the sheet according to the curling correction amount input by the input unit with respect to each sheet feed unit.
 7. The sheet processing apparatus according to claim 5, further comprising a notifying unit configured to notify a user of the sheet feed unit specified by the specifying unit, wherein the notifying unit is configured to notify the user of the sheet feed unit specified by the specifying unit by displaying a notification screen on a display unit, and wherein the input unit is configured to input the curling correction amount via the notification screen displayed on the display unit.
 8. The sheet processing apparatus according to claim 1, further comprising an image forming unit configured to form an image on the sheet fed from any one of the plurality of sheet feed units, wherein the curl detecting unit is configured to detect curling that has occurred due to image forming processing by the image forming unit.
 9. A method for controlling a sheet processing apparatus configured to convey a sheet fed from any one of a plurality of sheet feed units, the method comprising: detecting curling of the sheet fed from any one of the plurality of sheet feed units; and specifying a sheet feed unit that has fed the sheet having the detected curling from among the plurality of sheet feed units.
 10. The method according to claim 9, further comprising notifying a user of the specified sheet feed unit.
 11. The method according to claim 10, further comprising: discharging the sheet fed from any one of the plurality of sheet feed units to a sheet discharge unit; if the curling of the sheet has been detected, specifying the sheet feed unit that has fed the sheet having the detected curling and a sheet feed unit that has fed the sheet existing in the sheet discharge unit; and notifying the user of the specified sheet feed unit.
 12. The method according to claim 11, further comprising: determining whether a stacking amount of sheets existing in the sheet discharge unit has reached a predetermined value; and if it is determined that the stacking amount of sheets existing in the sheet discharge unit has reached the predetermined value and the curling of the sheet has been detected, notifying the user of the specified sheet feed unit.
 13. The method according to claim 9, further comprising correcting the curling of the sheet according to a curling correction amount input by an input unit configured to input the curling correction amount for correcting curling of the sheet.
 14. The method according to claim 13, further comprising: inputting the curling correction amount with respect to each sheet feed unit of the plurality of sheet feed units via the input unit; and correcting the curling of the sheet according to the curling correction amount input with respect to each sheet feed unit.
 15. The method according to claim 13, further comprising: notifying a user of the specified sheet feed unit by displaying a notification screen on a display unit; and inputting the curling correction amount via the notification screen displayed on the display unit.
 16. The method according to claim 9, further comprising: forming an image on the sheet fed from any one of the plurality of sheet feed units; and detecting curling that has occurred due to the image forming processing.
 17. A computer-readable storage medium storing instructions which, when executed by a sheet processing apparatus configured to convey a sheet fed from any one of a plurality of sheet feed units, cause the sheet processing apparatus to perform operations comprising: detecting curling of the sheet fed from any one of the plurality of sheet feed units; and specifying a sheet feed unit that has fed the sheet having the detected curling from among the plurality of sheet feed units. 